New signs of climate change: shifting seasons, warmer Antarctica

The news might seem welcome in the middle of a long, cold winter: Scientists have shown that the start of spring has moved almost two days earlier in the last 50 years.

But scientists say the finding, one of two papers released today on climate change, is actually a warning sign. Together, the studies bolster the argument that the planet's temperatures have shifted significantly in the last half-century, with many of the potential consequences likely to be negative.

Reporting in the scientific journal Nature, two teams of scientists presented evidence that all seasons are occurring earlier worldwide and that more of Antarctica is showing signs of warming than had been thought.

The seasonal study, from the University of California- Berkeley and Harvard University, compared temperature data in regions around the world to the distance between the sun and Earth at various points in time.

The information showed that warming temperatures associated with spring, as well as autumnal cooling, have moved forward by 1.7 days from 1954 to 2007.Such a shift is not seen anywhere else in temperature records stretching back to the 19th Century, and much of the change appears to have occurred since 1981, said the lead author, Berkeley graduate student Alexander Stine.

"Really, the last 27 years stand out as being different from anywhere previous in the record," Stine said.

The other report, led by University of Washington climatologist Eric Steig, addresses previous observations that only the northwestern peninsula of Antarctica has shown significant warming over the last 40 years, while the bulk of the continent appeared to be cooling.

Those measurements were fixed on by climate change skeptics who are unconvinced that the planet is undergoing a universal warming trend.

But by adding satellite data to temperatures collected from weather stations in Antarctica from 1957 to 2006, Steig's team found that a large portion of western Antarctica has been warming at a rate of 0.17 degrees Celsius per decade, roughly double the global warming rate in the last century.

Steig cautioned that the limitations of the data make it hard to predict future temperature changes in the region. But if warming is occurring across a wider area than previously observed, that could increase the possibility of large ice shelves melting off the continent and changing sea levels around the world.

"This study showing warming means we can't be complacent about thinking the West Antarctica ice sheet is invulnerable," Steig said. "It will eventually melt if warming like this continues."